Biometrics

Fission

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Biometrics are local device authentication. The host may use face recognition, fingerprint, iris, or the device credential fallback. The result says the current device user passed the local policy; it is not a server identity proof.

This reference is for the exact API shape. If you are wiring the feature into an app for the first time, start with the Biometrics guide, then return here when you need operation names, request types, provider contracts, or platform configuration details.

Public API

Item	Value
Effect helper or entrypoint	ctx.effects.biometrics()
Provider trait or host contract	BiometricHost
Test provider or test entrypoint	MemoryBiometricHost
Primary request types	BiometricAuthenticateRequest
Primary success types	BiometricAvailability / BiometricAuthenticateResult
Error type	BiometricError
CLI value	biometric

Operations

Method or operation	Purpose	Request	Success
availability	Query support, enrollment, available modalities, and credential fallback.	()	BiometricAvailability
authenticate	Show a local authentication prompt.	BiometricAuthenticateRequest	BiometricAuthenticateResult
cancel_authentication	Cancel the active prompt where the host permits it.	()	()

Provider contract

Register a BiometricHost with .with_biometric_host(...). Use MemoryBiometricHost for tests. A real host should distinguish unsupported hardware, no enrollment, cancellation, denied permission, and failed verification.

Providers should return typed errors for unsupported operations, denied permissions, unavailable hardware, cancellation, timeouts, and platform policy restrictions. Silent success is not acceptable because reducers need a truthful result to update state and explain what happened.

Platform configuration

The CLI adds Android biometric permissions and the iOS Face ID usage string. macOS and Windows support local authentication through host providers. Web fingerprint prompts are normally passkeys/WebAuthn rather than raw biometric access.

When a CLI value exists, fission add-capability <value> --project-dir . records the capability in fission.toml and updates generated target files where Fission can do that deterministically. Android generated configuration lives in platforms/android/AndroidManifest.xml. iOS generated configuration lives in platforms/ios/Info.plist and platforms/ios/Entitlements.plist when entitlements are required. Desktop package metadata is reviewed during packaging because Windows, macOS, and Linux use different permission and distribution systems.

Runtime behavior

Capability calls are queued from reducers through ctx.effects. The active shell resolves the request with the registered provider and then dispatches the configured success or error action. Missing providers should produce typed unsupported errors. Packaging mistakes usually show up as denied permissions, missing entitlements, missing route registration, or provider-specific failures.

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Biometrics guide

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Capability matrix

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Platform capabilities reference